Optimal selection of input torque considering battery utilization for a hybrid electric vehicle

Abstract

A preferred input torque for a hybrid powertrain is determined within a solution space of feasible input torques in accordance with a plurality of powertrain system constraints that results in a minimum overall powertrain system loss. System power losses and battery utilization costs are calculated at feasible input torques and a solution for the input torque corresponding to the minimum total powertrain system loss is converged upon to determine the preferred input torque.

1. Method for establishing a preferred operating point for a preselected powertrain operating parameter in a powertrain system having an energy storage system (ESS), comprising:
 determining a feasible operating space for the preselected powertrain operating parameter and within said operating space determining corresponding ESS power and system power loss; 
 determining a total system loss by applying an ESS power utilization cost as function of ESS power to the system power loss; 
 searching the feasible operating space for a value of the operating parameter corresponding to a minimum total system loss; and 
 establishing the preferred operating point as the value in the operating parameter corresponding to the minimum total system loss. 
 
     
     
       2. The method of  claim 1 , wherein said preselected powertrain parameter comprises an input torque. 
     
     
       3. The method of  claim 1 , wherein said powertrain system includes an internal combustion engine, a transmission and an electric machine, and wherein the ESS comprises a battery. 
     
     
       4. The method of  claim 1 , wherein the ESS power utilization cost is a function of at least one ESS parameter. 
     
     
       5. The method of  claim 4 , wherein the at least one ESS parameter comprises a state of charge of the ESS, an amp-hour throughput of the ESS and ESS power. 
     
     
       6. The method of  claim 1 , wherein determined a total system loss by applying an ESS power utilization cost as a function of ESS power to the system power loss further comprises:
 determining a value of at least one ESS parameter; 
 determining the ESS power utilization cost as a function of the at least one ESS parameter; and 
 adding the ESS power utilization cost to the system power loss to determine the total system loss. 
 
     
     
       7. The method of  claim 6 , wherein the at least one ESS parameter comprises a state of charge of the ESS and an amp-hour throughput of the ESS. 
     
     
       8. The method of  claim 1 , wherein the system power loss is determined from a plurality of sub-system power losses. 
     
     
       9. The method of  claim 1 , wherein searching the feasible operating space for the operating point corresponding to the minimum total system loss comprises performing a section search utilizing a golden section ratio. 
     
     
       10. Method for establishing a preferred operating point for a preselected powertrain operating parameter in a powertrain system having an energy storage system (ESS), comprising:
 determining a feasible operating space for the preselected powertrain operating parameter and within said operating space determining corresponding ESS power and system power loss; 
 applying an ESS power utilization cost as function of ESS power to the system power loss to determine a total system loss; 
 searching the feasible operating space for a value of the operating parameter corresponding to a minimum total system loss; and 
 establishing the preferred operating point as the value in the operating parameter corresponding to the minimum total system loss; 
 wherein applying an ESS power utilization cost as a function of ESS power to the system power loss to determine a total system loss, further comprises: 
 determining a value of at least one ESS parameter; 
 determining the ESS power utilization cost as a function of the at least one ESS parameter: and 
 adding the ESS power utilization cost to the system power loss to determine the total system loss; 
 wherein the at least one ESS parameter comprises a state of charge of the ESS and an amp-hour throughput of the ESS; 
 wherein determining the ESS power utilization cost as a function of the at least one ESS parameter, further comprises: 
 determining an ESS power utilization cost factor as a function of the state of charge and the amp-hour throughput; and 
 multiplying ESS power by the ESS power utilization cost factor to determine the ESS power utilization cost. 
 
     
     
       11. The method of  claim 10 , further comprising:
 shifting the ESS power by a shift value to a shifted ESS power, wherein the shift value is a function of the state of charge, and wherein multiplying the ESS power by the ESS cost factor utilizes the shifted ESS power. 
 
     
     
       12. The method of  claim 11 , wherein the shift value is a function of the state of charge such that at low states of charge the total system power loss is biased in a manner to effect reduced ESS power and at high states of charge the total system loss is biased in a manner to effect increased ESS power. 
     
     
       13. Method for establishing a preferred operating point for a preselected powertrain operating parameter in a powertrain system having an energy storage system (ESS), comprising:
 determining a feasible operating space for the preselected powertrain operating parameter and within said operating space determining corresponding ESS power and system power loss; 
 applying an ESS power utilization cost as function of ESS power to the system power loss to determine a total system loss; 
 searching the feasible operating space for a value of the operating parameter corresponding to a minimum total system loss; and 
 establishing the preferred operating point as the value in the operating parameter corresponding to the minimum total system loss; 
 wherein said preferred operating point is periodically updated, and further wherein such periodic update proceeds during quiescent powertrain operation only when the value for the most recent search corresponds to a respective minimum total system loss that is at least a predetermined amount less than the respective minimum total system loss corresponding to the previously established preferred operating point.